Systems, articles, and methods for capacitive electromyography sensors

ABSTRACT

Systems, articles, and methods for improved capacitive electromyography (“EMG”) sensors are described. The improved capacitive EMG sensors include one or more sensor electrode(s) that is/are coated with a protective barrier formed of a material that has a relative permittivity εr of about 10 or more. The protective barrier shields the sensor electrode(s) from moisture, sweat, skin oils, etc. while advantageously contributing to a large capacitance between the sensor electrode(s) and the user&#39;s body. In this way, the improved capacitive EMG sensors provide enhanced robustness against variations in skin and/or environmental conditions. Such improved capacitive EMG sensors are particularly well-suited for use in wearable EMG devices that may be worn by a user for an extended period of time and/or under a variety of skin and/or environmental conditions. A wearable EMG device that provides a component of a human-electronics interface and incorporates such improved capacitive EMG sensors is described.

BACKGROUND Technical Field

The present systems, articles, and methods generally relate toelectromyography and particularly relate to capacitive electromyographysensors.

Description of the Related Art Wearable Electronic Devices

Electronic devices are commonplace throughout most of the world today.Advancements in integrated circuit technology have enabled thedevelopment of electronic devices that are sufficiently small andlightweight to be carried by the user. Such “portable” electronicdevices may include on-board power supplies (such as batteries or otherpower storage systems) and may be designed to operate without anywire-connections to other electronic systems; however, a small andlightweight electronic device may still be considered portable even ifit includes a wire-connection to another electronic system. For example,a microphone may be considered a portable electronic device whether itis operated wirelessly or through a wire-connection.

The convenience afforded by the portability of electronic devices hasfostered a huge industry. Smartphones, audio players, laptop computers,tablet computers, and ebook readers are all examples of portableelectronic devices. However, the convenience of being able to carry aportable electronic device has also introduced the inconvenience ofhaving one's hand(s) encumbered by the device itself. This problem isaddressed by making an electronic device not only portable, butwearable.

A wearable electronic device is any portable electronic device that auser can carry without physically grasping, clutching, or otherwiseholding onto the device with their hands. For example, a wearableelectronic device may be attached or coupled to the user by a strap orstraps, a band or bands, a clip or clips, an adhesive, a pin and clasp,an article of clothing, tension or elastic support, an interference fit,an ergonomic form, etc. Examples of wearable electronic devices includedigital wristwatches, electronic armbands, electronic rings, electronicankle-bracelets or “anklets,” head-mounted electronic display units,hearing aids, and so on.

Human-Electronics Interfaces

A wearable electronic device may provide direct functionality for a user(such as audio playback, data display, computing functions, etc.) or itmay provide electronics to interact with, receive information from, orcontrol another electronic device. For example, a wearable electronicdevice may include sensors that are responsive to (i.e., detect andprovide one or more signal(s) in response to detecting) inputs effectedby a user and transmit signals to another electronic device based onthose inputs. Sensor-types and input-types may each take on a variety offorms, including but not limited to: tactile sensors (e.g., buttons,switches, touchpads, or keys) providing manual control, acoustic sensorsproviding voice-control, electromyography sensors providing gesturecontrol, and/or accelerometers providing gesture control.

A human-computer interface (“HCI”) is an example of a human-electronicsinterface. The present systems, articles, and methods may be applied toHCIs, but may also be applied to any other form of human-electronicsinterface.

Electromyography Sensors

Electromyography (“EMG”) is a process for detecting and processing theelectrical signals generated by muscle activity. EMG devices employ EMGsensors that are responsive to the range of electrical potentials(typically μV-mV) involved in muscle activity. EMG signals may be usedin a wide variety of applications, including: medical monitoring anddiagnosis, muscle rehabilitation, exercise and training, prostheticcontrol, and even in controlling functions of electronic devices.

There are two main types of EMG sensors: intramuscular EMG sensors andsurface EMG sensors. As the names suggest, intramuscular EMG sensors aredesigned to penetrate the skin and measure EMG signals from within themuscle tissue, while surface EMG sensors are designed to rest on anexposed surface of the skin and measure EMG signals from there.Intramuscular EMG sensor measurements can be much more precise thansurface EMG sensor measurements; however, intramuscular EMG sensors mustbe applied by a trained professional, are obviously more invasive, andare less desirable from the patient's point of view. The use ofintramuscular EMG sensors is generally limited to clinical settings.

Surface EMG sensors can be applied with ease, are much more comfortablefor the patient/user, and are therefore more appropriate fornon-clinical settings and uses. For example, human-electronicsinterfaces that employ EMG, such as those proposed in U.S. Pat. No.6,244,873 and U.S. Pat. No. 8,170,656, usually employ surface EMGsensors. Surface EMG sensors come in two forms: resistive EMG sensorsand capacitive EMG sensors. For both forms of surface EMG sensors, thesensor electrode typically includes a plate of electrically conductivematerial that is placed against or in very close proximity to theexposed surface of the user's skin. A resistive EMG sensor electrode istypically directly electrically coupled to the user's skin while acapacitive EMG sensor electrode is typically capacitively coupled to theuser's skin. In either case, skin and/or environmental conditions, suchas hair density, humidity and moisture levels, and so on, can have asignificant impact on the performance of the sensor. These parametersare generally controlled for resistive EMG sensors by preparing theuser's skin before applying the sensor electrodes. For example, theregion of the user's skin where a resistive electrode is to be placed isusually shaved, exfoliated, and slathered with a conductive gel toestablish a suitable and stable environment before the resistiveelectrode is applied. This obviously limits the appeal of resistive EMGsensors to users, in particular for home and/or recreational use.Capacitive EMG sensors are advantageous because they are generally morerobust against some skin and environmental conditions, such as hairdensity, and are typically applied without the elaborate skinpreparation measures (e.g., shaving, exfoliating, and applying aconductive gel) that are employed for resistive sensors. However,capacitive EMG sensors are still very sensitive to moisture andperformance can degrade considerably when, for example, a user sweats.There is a need in the art for capacitive EMG sensors with improvedrobustness against variations in skin and/or environmental conditions.

BRIEF SUMMARY

A capacitive electromyography (“EMG”) sensor may be summarized asincluding a substrate; a first sensor electrode carried by thesubstrate, wherein the first sensor electrode comprises an electricallyconductive plate having a first surface that faces the substrate and asecond surface that is opposite the first surface; circuitrycommunicatively coupled to the first sensor electrode; and a dielectriclayer formed of a dielectric material that has a relative permittivityof at least about 10, wherein the dielectric layer coats the secondsurface of the first sensor electrode. The first sensor electrode may beformed of a material including copper. The circuitry may include atleast one circuit selected from the group consisting of: anamplification circuit, a filtering circuit, and an analog-to-digitalconversion circuit. At least a portion of the circuitry may be carriedby the substrate. The substrate may include a first surface and a secondsurface, the second surface opposite the first surface across athickness of the substrate, and the at least a portion of the circuitrymay be carried by the first surface of the substrate and the firstsensor electrode may be carried by the second surface of the substrate.The dielectric layer may include a ceramic material. The dielectriclayer may include an X7R ceramic material. The substrate, the firstsensor electrode, and the dielectric layer may constitute a laminatestructure. The capacitive EMG sensor may further include an electricallyconductive epoxy sandwiched in between the dielectric layer and thefirst sensor electrode, wherein the dielectric layer is adhered to thefirst sensor electrode by the electrically conductive epoxy.Alternatively, the capacitive EMG sensor may further include anelectrically conductive solder sandwiched in between the dielectriclayer and the first sensor electrode, wherein the dielectric layer isadhered to the first sensor electrode by the electrically conductivesolder. The dielectric layer may have a thickness of less than about 10micrometers. The capacitive EMG sensor may be a differential capacitiveEMG sensor that further includes a second sensor electrode carried bythe substrate, the second sensor electrode comprising an electricallyconductive plate having a first surface that faces the substrate and asecond surface that is opposite the first surface across a thickness ofthe second sensor electrode, wherein the second sensor electrode iscommunicatively coupled to the circuitry, and wherein the dielectriclayer coats the second surface of the second sensor electrode. Thedielectric layer may comprise a single continuous layer of dielectricmaterial that coats both the second surface of the first sensorelectrode and the second surface of the second sensor electrode. Thedielectric layer may comprise a first section that coats the secondsurface of the first sensor electrode and at least a second section thatcoats the second surface of the second sensor electrode, wherein thefirst section of the dielectric layer is physically separate from thesecond section of the dielectric layer. The first sensor electrode andthe second sensor electrode may be substantially coplanar. Thecapacitive EMG sensor may further include a ground electrode carried bythe substrate, the ground electrode comprising an electricallyconductive plate having a first surface that faces the substrate and asecond surface that is opposite the first surface across a thickness ofthe ground electrode, wherein the ground electrode is communicativelycoupled to the circuitry, and wherein the second surface of the groundelectrode is exposed and not coated by the dielectric layer. Thecapacitive EMG sensor may further include at least one additional layerthat is sandwiched in between the first sensor electrode and thesubstrate.

A method of fabricating a capacitive EMG sensor may be summarized asincluding forming at least a portion of at least one circuit on a firstsurface of a substrate; forming a first sensor electrode on a secondsurface of the substrate, the second surface of the substrate oppositethe first surface of the substrate across a thickness of the substrate,wherein the first sensor electrode comprises an electrically conductiveplate; forming at least one electrically conductive pathway thatcommunicatively couples the first sensor electrode and the at least aportion of at least one circuit; and coating the first sensor electrodewith a dielectric layer comprising a dielectric material that has arelative permittivity of at least about 10. Coating the first sensorelectrode with a dielectric layer may include coating at least a portionof the second surface of the substrate with the dielectric layer.Coating the first sensor electrode with a dielectric layer may includecoating the first sensor electrode with a ceramic material. Coating thefirst sensor electrode with a dielectric layer may include coating thefirst sensor electrode with an X7R ceramic material. The capacitive EMGsensor may be a differential capacitive EMG sensor and the method mayfurther include forming a second sensor electrode on the second surfaceof the substrate, wherein the second sensor electrode comprises anelectrically conductive plate; forming at least one electricallyconductive pathway that communicatively couples the second sensorelectrode and the at least a portion of at least one circuit; andcoating the second sensor electrode with the dielectric layer. Themethod may further include forming a ground electrode on the secondsurface of the substrate, wherein the ground electrode comprises anelectrically conductive plate; and forming at least one electricallyconductive pathway that communicatively couples the ground electrode andthe at least a portion of at least one circuit. Coating the first sensorelectrode with a dielectric layer may include selectively coating thefirst sensor electrode with the dielectric layer and not coating theground electrode with the dielectric layer. Coating the first sensorelectrode with a dielectric layer may include coating both the firstsensor electrode and the ground electrode with the dielectric layer, andthe method may further include forming a hole in the dielectric layer toexpose the ground electrode. Coating the first sensor electrode with adielectric layer may include depositing a layer of electricallyconductive epoxy on the first sensor electrode; and depositing thedielectric layer on the layer of electrically conductive epoxy. Coatingthe first sensor electrode with a dielectric layer may includedepositing a layer of electrically conductive solder on the first sensorelectrode; and depositing the dielectric layer on the layer ofelectrically conductive solder.

A wearable EMG device may be summarized as including at least onecapacitive EMG sensor responsive to (i.e., to detect and provide one ormore signal(s) in response to detecting) muscle activity correspondingto a gesture performed by a user of the wearable EMG device, wherein inresponse to muscle activity corresponding to a gesture performed by auser of the wearable EMG device, the at least one capacitive EMG sensorprovides at least one signal, and wherein the at least one capacitiveEMG sensor includes: a first sensor electrode comprising an electricallyconductive plate; and a dielectric layer formed of a dielectric materialthat has a relative permittivity of at least about 10, wherein thedielectric layer coats the first sensor electrode; a processorcommunicatively coupled to the at least one capacitive EMG sensor to inuse process signals provided by the at least one capacitive EMG sensor;and an output terminal communicatively coupled to the processor totransmit signals output by the processor. The dielectric layer mayinclude a ceramic material. The ceramic material may include an X7Rceramic material. The wearable EMG device may further include circuitrythat mediates communicative coupling between the at least one capacitiveEMG sensor and the processor, wherein the circuitry includes at leastone circuit selected from the group consisting of: an amplificationcircuit, a filtering circuit, and an analog-to-digital conversioncircuit. The dielectric layer of the at least one capacitive EMG sensormay have a thickness of less than about 10 micrometers. The at least onecapacitive EMG sensor may include at least one differential capacitiveEMG sensor, and the at least one differential capacitive EMG sensor mayfurther include a second sensor electrode comprising an electricallyconductive plate, wherein the dielectric layer coats the second sensorelectrode. The at least one capacitive EMG sensor may further include aground electrode comprising an electrically conductive plate, whereinthe ground electrode is exposed and not coated by the dielectric layer.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

In the drawings, identical reference numbers identify similar elementsor acts. The sizes and relative positions of elements in the drawingsare not necessarily drawn to scale. For example, the shapes of variouselements and angles are not drawn to scale, and some of these elementsare arbitrarily enlarged and positioned to improve drawing legibility.Further, the particular shapes of the elements as drawn are not intendedto convey any information regarding the actual shape of the particularelements, and have been solely selected for ease of recognition in thedrawings.

FIG. 1 is a cross-sectional view of an improved capacitive EMG sensorthat provides enhanced robustness against variations in skin and/orenvironmental conditions in accordance with the present systems,articles, and methods.

FIG. 2 is a cross-sectional view of a laminate version of an improvedcapacitive EMG sensor that provides enhanced robustness againstvariations in skin and/or environmental conditions in accordance withthe present systems, articles, and methods.

FIG. 3 is a flow-diagram showing a method of fabricating an improvedcapacitive EMG sensor in accordance with the present systems, articles,and methods.

FIG. 4 is a perspective view of an exemplary wearable EMG device thatincludes improved capacitive EMG sensors in accordance with the presentsystems, articles, and methods.

DETAILED DESCRIPTION

In the following description, certain specific details are set forth inorder to provide a thorough understanding of various disclosedembodiments. However, one skilled in the relevant art will recognizethat embodiments may be practiced without one or more of these specificdetails, or with other methods, components, materials, etc. In otherinstances, well-known structures associated with electric circuits, andin particular printed circuit boards, have not been shown or describedin detail to avoid unnecessarily obscuring descriptions of theembodiments.

Unless the context requires otherwise, throughout the specification andclaims which follow, the word “comprise” and variations thereof, suchas, “comprises” and “comprising” are to be construed in an open,inclusive sense, that is as “including, but not limited to.”

Reference throughout this specification to “one embodiment” or “anembodiment” means that a particular feature, structures, orcharacteristics may be combined in any suitable manner in one or moreembodiments.

As used in this specification and the appended claims, the singularforms “a,” “an,” and “the” include plural referents unless the contentclearly dictates otherwise. It should also be noted that the term “or”is generally employed in its broadest sense, that is as meaning “and/or”unless the content clearly dictates otherwise.

The headings and Abstract of the Disclosure provided herein are forconvenience only and do not interpret the scope or meaning of theembodiments.

The various embodiments described herein provide systems, articles, andmethods for capacitive EMG sensors with improved robustness againstvariations in skin and/or environmental conditions. In particular, thepresent systems, articles, and methods describe capacitive EMG sensordesigns that employ at least one capacitive electrode having aprotective coating that provides a barrier to moisture and a highrelative permittivity ε_(r). These capacitive EMG sensor designs may beused in any device or method involving capacitive EMG sensing, thoughthey are particularly well-suited for use in applications involvinglong-term coupling to a user's body over a range of evolving skin and/orenvironmental conditions. An example application in a wearable EMGdevice that forms part of a human-electronics interface is described.

Throughout this specification and the appended claims, the terms“coating” and “coat,” and variants thereof, are used both as nouns andas verbs to indicate a relationship (noun) or the formation of arelationship (verb) in which a layer of material overlies, underlies, orgenerally “covers” at least a portion of a device or component, eitherdirectly or through one or more intervening layers.

FIG. 1 is a cross-sectional view of an example of an improved capacitiveEMG sensor 100 that provides enhanced robustness against variations inskin and/or environmental conditions in accordance with the presentsystems, articles, and methods. Exemplary sensor 100 is a differentialcapacitive EMG sensor that includes two capacitive sensor electrodes 121and 131, though the teachings described herein are also applicable tosingle-ended sensor systems that employ only a single capacitive sensorelectrode (i.e., one of sensor electrodes 121 or 131). Differentialsensor 100 comprises a substrate 101 having a first surface 101 a and asecond surface 101 b opposite the first surface 101 a across a thicknessof substrate 101. First surface 101 a carries at least a portion of atleast one circuit (generally, circuitry 110) and second surface 101 bcarries first sensor electrode 121, second sensor electrode 131, and aground electrode 140. As will be described in more detail later,circuitry 110 may include at least a portion of at least one electricalor electronic circuit to process signals provided by first and secondsensor electrodes 121, 131, including, for example, at least a portionof at least one amplification circuit, at least a portion of at leastone filtering circuit, and/or at least a portion of at least oneanalog-to-digital conversion circuit.

First sensor electrode 121 includes an electrically conductive plateformed of an electrically conductive material (such as, for example,copper or a material including copper) and has a first surface 121 a anda second surface 121 b, second surface 121 b being opposite firstsurface 121 a across a thickness of electrode 121. First sensorelectrode 121 is carried by second surface 101 b of substrate 101 suchthat first surface 121 a of first sensor electrode 121 faces secondsurface 101 b of substrate 101. Throughout this specification and theappended claims, the terms “carries” and “carried by” are generally usedto describe a spatial relationship in which a first layer/component ispositioned proximate and physically coupled to a surface of a secondlayer/component, either directly or through one or more interveninglayers/components. For example, circuitry 110 is carried by firstsurface 101 a of substrate 101 and first sensor electrode 121 is carriedby second surface 101 b of substrate 101. Circuitry 110 is directlycarried by first surface 101 a of substrate 101 because there are nointervening layers/components that mediate the physical coupling betweencircuitry 110 and first surface 101 a of substrate 101; however,circuitry 110 would still be considered “carried by” first surface 101 aof substrate 101 even if the physical coupling between circuitry 110 andfirst surface 101 a of substrate 101 was mediated by at least oneintervening layer/component. The terms “carries” and “carried by” arenot intended to denote a particular orientation with respect to top andbottom and/or left and right.

First sensor electrode 121 is communicatively coupled to circuitry 110by at least one electrically conductive pathway 151, which in theillustrated example of FIG. 1 is realized by a via connection thatextends through substrate 101.

In accordance with the present systems, articles, and methods, firstsensor electrode 121 is coated by a dielectric layer 123 formed of amaterial that has a relative permittivity ε_(r) of at least 10, and byan adhesive layer 122 that is sandwiched in between first sensorelectrode 121 and dielectric layer 123. Adhesive layer 122 serves toadhere, affix, or otherwise couple dielectric layer 123 to the secondsurface 121 b of first sensor electrode 121, and may comprise, forexample, an electrically conductive epoxy or an electrically conductivesolder. In other words, adhesive layer 122 mediates physical andelectrical coupling between dielectric layer 123 and first sensorelectrode 121. Referring back to the definition of the terms “carries”and “carried by,” both adhesive layer 122 and dielectric layer 123 areconsidered to be carried by second surface 101 b of substrate 101.

Dielectric layer 123 may comprise any dielectric material that has alarge relative permittivity ε_(r) (e.g., a relative permittivity ofabout 10 or more, including a relative permittivity of about 10, about20, about 50, about 100, about 1000, etc.). Advantageously, dielectriclayer 123 may comprise a ceramic material, such as an X7R ceramicmaterial. Throughout this specification and the appended claims, theterm “X7R” refers to the EIA RS-198 standard three-digit code fortemperature ranges and inherent change of capacitance. Specifically, thecode “X7R” indicates a material that will operate in the temperaturerange of −55° C. to +125° C. with a change of capacitance of ±15%. Aperson of skill in the art will appreciate that the X7R EIA code issubstantially equivalent to “2X1” under the IEC/EN 60384-9/22 standard.Dielectric layer 123 may comprise a resin and/or ceramic powder such asthose used in FaradFlex® products available from Oak-MitsuiTechnologies.

Since capacitive EMG sensor 100 is differential, it includes a secondsensor electrode 131. Second sensor electrode 131 may be substantiallysimilar to first sensor electrode 121 in that second sensor electrode131 includes an electrically conductive plate formed of an electricallyconductive material (e.g., a material including copper) that has a firstsurface 131 a and a second surface 131 b, second surface 131 b beingopposite first surface 131 a across a thickness of electrode 131. Secondsensor electrode 131 is carried by second surface 101 b of substrate 101such that first surface 131 a of second sensor electrode 131 facessecond surface 101 b of substrate 101. Second sensor electrode 131 isalso coated by a dielectric layer 133 that is substantially similar todielectric layer 123, and dielectric layer 133 is adhered, affixed, orotherwise coupled to second surface 131 b of second sensor electrode 131by an adhesive layer 132 that is substantially similar to adhesive layer122. Second sensor electrode 131 is communicatively coupled to circuitry110 by at least one electrically conductive pathway 152, which in theillustrated example of FIG. 1 is realized by a via connection thatextends through substrate 101. As is the case for the illustratedexample of FIG. 1, first sensor electrode 121 and second sensorelectrode 131 may be substantially coplanar.

Capacitive EMG sensor 100 also includes a ground electrode 140. Groundelectrode 140 includes an electrically conductive plate formed of anelectrically conductive material (e.g., the same material that makes upfirst sensor electrode 121 and second sensor electrode 131) that has afirst surface 141 a and a second surface 141 b, second surface 141 bbeing opposite first surface 141 a across a thickness of electrode 140.Ground electrode 140 is carried by second surface 101 b of substrate 101such that first surface 140 a of ground electrode 140 faces secondsurface 101 b of substrate 101. Ground electrode 140 is communicativelycoupled to circuitry 110 by at least one electrically conductive pathway153, which in the illustrated example of FIG. 1 is realized by a viaconnection that extends through substrate 101. Unlike second surface 121b of first sensor electrode 121 and second surface 131 b of secondsensor electrode 131, second surface 140 b of ground electrode 140 isexposed and not coated by a dielectric layer in order that groundelectrode 140 may advantageously provide a directly electrically coupled(i.e., resistively coupled) path to ground.

In use, capacitive EMG sensor 100 is positioned proximate a user'smuscle(s) so that dielectric layers 123, 133 and ground electrode 140are all in physical contact with the user's skin (or, in some cases, alayer of material such as clothing may mediate physical contact betweensensor 100 and the user's skin). Dielectric layers 123, 133 areadvantageously formed of a dielectric material that has a high relativepermittivity (e.g., ε_(r) greater than or equal to about 10) in order toenhance the capacitive coupling between sensor electrodes 121, 131 andthe user's body. For each of first sensor electrode 121 and secondsensor electrode 131, the respective capacitance that couples the sensorelectrode (121, 131) to the user's body (e.g., skin) is at leastapproximately given by equation 1:

$\begin{matrix}{C = \frac{ɛ_{r}ɛ_{0}A}{d}} & (1)\end{matrix}$

where ε_(r) is the relative permittivity of the dielectric material thatcoats the sensor electrode (i.e., dielectric layers 123, 133), ε_(o) isthe vacuum permittivity (i.e., a constant value of 8.8541878176×10⁻¹²F/m), A is the area of the sensor electrode, and d is the distancebetween the sensor electrode and the user's body. Thus, if A and d areheld constant, ε_(r) (i.e., the relative permittivity of dielectriclayers 123, 133) directly influences the capacitance between the user'sbody and each of first sensor electrode 121 and second sensor electrode131. A large ε_(r) may enable a capacitive EMG sensor to employ smallersensor electrode area(s) A and/or greater separation d between thesensor electrode(s) and the user's body.

Dielectric layers 123, 133 are advantageously bio-compatible (e.g.,non-toxic, etc.) and substantially robust against the corrosive effectsof sweat and skin oils. Dielectric layers 123, 133 are alsoadvantageously non-absorptive and impermeable to water, sweat, and skinoils. Ideally, dielectric layers 123, 133 provide hermetic barriersbetween the user's skin and first and second sensor electrodes 121, 131such that the presence of sweat, water, and/or skin oils does notsubstantially degrade the performance of capacitive EMG sensor 100.

Even though dielectric layers 123, 133 may protect first sensorelectrode 121 and second sensor electrode 131 (respectively) frommoisture and/or other aspects of the user's skin, such moisture and/orother aspects that may underlie dielectric layers 123, 133 (e.g., sweator skin oils that may mediate coupling between the user's body anddielectric layers 123, 133) may still affect the capacitive couplingbetween the user's body and first and second sensor electrodes 121, 131.This is a further reason why it is advantageous for dielectric layers123, 133 to be formed of a dielectric material that has a high relativepermittivity (i.e., ε_(r)≥10): the larger the relative permittivity ofdielectric layers 123, 133, the larger the capacitance that couples theuser's body to first and second sensor electrodes 121, 131 and thesmaller the proportionate impact of variations in sweat or skin oilconditions.

Equation 1 shows that the capacitance C that couples the user's body tofirst and second sensor electrodes 121, 131 is directly proportional tothe relative permittivity ε_(r) and inversely proportional to thethickness d of dielectric layers 123, 133. Thus, while it isadvantageous for dielectric layers 123, 133 to be formed of a dielectricmaterial that has a high relative permittivity ε_(r), it is similarlyadvantageous for dielectric layers 123, 133 to be relatively thin (i.e.,for d to be small). In accordance with the present systems, articles,and methods, the thickness of dielectric layers 123, 133 may be, forexample, approximately 10 μm or less. Approximately 10 μm or less issufficiently thick to provide an adequate barrier to moisture (e.g.,sweat/oil) and electrical insulation, and sufficiently thin to providean adequate capacitance C as per equation 1.

In accordance with the present systems, articles, and methods, groundelectrode 140 is exposed and not coated by a dielectric layer. This isbecause it is advantageous for ground electrode 140 to be resistivelycoupled to the user's body as opposed to capacitively coupled thereto inorder to provide a lower impedance for return currents.

Even though first and second sensor electrodes 121, 131 are coated bydielectric layers 123, 133 (respectively) and ground electrode 140 isnot coated by a dielectric layer, dielectric layers 123, 133 and groundelectrode 140 may all still simultaneously contact a user's skin whencapacitive EMG sensor 100 is positioned on the user. This is because thesurface of the user's skin may have a curvature and/or the surface ofthe user's skin (and/or the flesh thereunder) may be elastic andcompressible such that dielectric layers 123, 133 can be “pressed” intothe user's skin with sufficient depth to enable physical contact betweenground electrode 140 and the user's skin. While not drawn to scale, inthe illustrated example of FIG. 1, dielectric layers 123, 133 are stillthinner than the electrically conductive plates that form first andsecond sensor electrodes 121, 131. For example, dielectric layers 123,133 may each have a thickness of less than about 10 μm while first andsecond sensor electrodes 121, 131 may each have a thickness of about 30μm or more.

There are many different ways in which dielectric layers 123, 133 may beapplied to coat first and second sensor electrodes 121, 131(respectively) and the specific structural configuration of thecorresponding capacitive EMG sensor may vary to reflect this. Inexemplary capacitive EMG sensor 100, dielectric layers 123, 133 havebeen individually and separately deposited on first and second sensorelectrodes 121, 131 (respectively). This may be achieved by, forexample, brushing a liquid or fluid form of the dielectric material thatconstitutes dielectric layers 123 and 133 over second surface 121 b offirst sensor electrode 121 and second surface 131 b of second sensorelectrode 131. In this case, dielectric layers 123, 133 may subsequentlybe hardened or cured (and adhesive layers 122, 132 may potentially notbe required). Alternatively, individual and separate sections of asubstantially solid or non-fluid form of the dielectric material thatconstitutes dielectric layers 123 and 133 may be sized and dimensionedto at least approximately match the respective areas of first and secondsensor electrodes 121, 131 and then respective ones of such sections maybe deposited on first and second sensor electrodes 121 and 131. Forexample, a first section of a dielectric material (having a highrelative permittivity) may be sized and dimensioned to at leastapproximately match the area of first sensor electrode 121 and thisfirst section of the dielectric material may be adhered, affixed, orotherwise coupled to first sensor electrode 121 by adhesive layer 122 toform dielectric layer 123. Likewise, a second section of the dielectricmaterial may be sized and dimensioned to at least approximately matchthe area of second sensor electrode 131 and adhered, affixed, orotherwise coupled to second sensor electrode 131 by adhesive layer 132to form dielectric layer 133.

As an alternative to the above examples of depositing dielectric layers121, 131 as individual, separate sections of dielectric material, asingle continuous piece of dielectric material may be deposited oversecond surface 101 b of substrate 101, first and second sensorelectrodes 121, 131, and optionally ground electrode 140. In this case,substrate 101, first and second sensors electrodes 121, 131, anddielectric layers 123, 133 may together constitute a laminate structure.In other words, dielectric layers 123, 133 may be applied to first andsecond sensor electrodes 121, 131 as lamination layers using alamination process. In fabrication processes in which dielectricmaterial coats ground electrode 140, the portion of dielectric materialthat coats ground electrode may subsequently be removed (e.g., by anetching process) to expose second surface 140 b of ground electrode 140.

FIG. 2 is a cross-sectional view of an exemplary laminate version of animproved capacitive EMG sensor 200 that provides enhanced robustnessagainst variations in skin and/or environmental conditions in accordancewith the present systems, articles, and methods. Exemplary sensor 200 isa differential capacitive EMG sensor that is substantially similar tosensor 100 from FIG. 1 in that sensor 200 includes a substrate 201(substantially similar to substrate 101 from sensor 100), circuitry 210(substantially similar to circuitry 110 from sensor 100), first andsecond capacitive sensor electrodes 221 and 231 (substantially similarto first and second sensor electrodes 121 and 131, respectively, fromsensor 100), and ground electrode 240 (substantially similar to groundelectrode 140 from sensor 100). Sensor 200 also includes a dielectriclayer 250 that coats first and second sensor electrodes 221, 231 in asimilar way to dielectric layers 123, 133 from sensor 100. Likedielectric layers 123 and 133, dielectric layer 250 is formed of adielectric material that has a large relative permittivity (i.e., ε_(r)greater than or equal to about 10). However, unlike dielectric layers123 and 133, dielectric layer 250 is deposited as a single continuouslayer that coats both first and second sensor electrodes 221, 231 andalso coats at least a portion of substrate 201. For example, sensor 200may be a laminate structure and dielectric layer 250 may be depositedusing a lamination process. The deposition of dielectric layer 250 mayinitially coat ground electrode 240, in which case ground electrode 240may subsequently be exposed by forming (e.g., etching) a hole 260 indielectric layer 250. Otherwise, a temporary mask may cover groundelectrode 240 during deposition of dielectric layer 250 to preventdielectric layer 250 from coating ground electrode 240 and hole 260 maybe left as a result when the mask is subsequently removed.

Dielectric layer 250 may be deposited to provide a desired thickness of,for example, less than about 10 μm measured from the interface withfirst and second sensor electrodes 221, 231. Though not illustrated inFIG. 2, an adhesive layer may be used to adhere, affix, or otherwisecouple dielectric layer 250 to any or all of substrate 201, firstelectrode 221, and/or second sensor electrode 231.

Various methods for fabricating an improved capacitive EMG sensor thatincludes at least one protective, high-ε_(r) dielectric barrier havebeen described. These methods are summarized and generalized in FIG. 3.

FIG. 3 is a flow-diagram showing a method 300 of fabricating an improvedcapacitive EMG sensor (e.g., sensor 100 and/or sensor 200) in accordancewith the present systems, articles, and methods. Method 300 includesfour acts 301, 302, 303, and 304, though those of skill in the art willappreciate that in alternative embodiments certain acts may be omittedand/or additional acts may be added. Those of skill in the art will alsoappreciate that the illustrated order of the acts is shown for exemplarypurposes only and may change in alternative embodiments.

At 301, at least a portion of at least one circuit is formed on a firstsurface of a substrate. The at least a portion of at least one circuitmay include one or more conductive traces and/or one or more electricalor electronic circuits, such as one or more amplification circuit(s),one or more filtering circuit(s), and/or one or more analog-to-digitalconversion circuit(s). As examples, sensor 100 from FIG. 1 includescircuitry 110 and sensor 200 from FIG. 2 includes circuitry 210. Formingat least a portion of at least one circuit may include one or morelithography process(es) and/or soldering one or more component(s) to thesubstrate.

At 302, a first sensor electrode is formed on a second surface of thesubstrate. The first sensor electrode may include an electricallyconductive plate formed of, for example, a material including copper. Asexamples, sensor 100 from FIG. 1 includes first sensor electrode 121 andsensor 200 from FIG. 2 includes first sensor electrode 221. Forming thefirst sensor electrode may include, for example, one or more lithographyprocess(es). As previously described, the order of the acts of method300 may change. For example, in some cases it may be advantageous toform the first sensor electrode per act 302 prior to forming the atleast a portion of circuitry per act 301.

At 303, at least one electrically conductive pathway thatcommunicatively couples the at least a portion of at least one circuitand the first sensor electrode is formed. The at least one electricallyconductive pathway may include at least one via through the substrate,at least one conductive trace, and/or at least one wiring component. Forexample, sensor 100 includes electrically conductive pathway 151 thatcommunicatively couples circuitry 110 to first sensor electrode 121. Insome implementations, all or a portion of a via (e.g., a hole oraperture with or without electrically conductive communicative paththerethrough) may be formed in the substrate before either or both ofacts 301 and/or 302.

At 304, the first sensor electrode is coated with a dielectric layercomprising a dielectric material that has a relative permittivity ε_(r)of at least 10. As previously described, the coating may be applied in avariety of different ways, including without limitation: brushing orotherwise applying a fluid form of the dielectric material on the firstsensor electrode and curing the dielectric material; adhering, affixing,or otherwise coupling a substantially non-fluid form of the dielectricmaterial to the first sensor electrode using, for example, an adhesivelayer such as an electrically conductive epoxy or an electricallyconductive solder; or depositing a single continuous layer of thedielectric material over both the first sensor electrode and at least aportion of the substrate using a lamination process or other dielectricdeposition process. When an adhesive layer is used, coating the firstsensor electrode with a dielectric layer may include depositing a layerof electrically conductive epoxy on the first sensor electrode anddepositing the dielectric layer on the layer of electrically conductiveepoxy, or depositing a layer of electrically conductive solder on thefirst sensor electrode and depositing the dielectric layer on the layerof electrically conductive solder. As examples, sensor 100 includesdielectric layer 123 that is adhered to first sensor electrode 121 byadhesive layer 122 and sensor 200 includes dielectric layer 250 that isdeposited over first sensor electrode 221 and substrate 201 to form alaminate structure. The dielectric layer may include a ceramic material,such as an X7R ceramic material.

In addition to acts 301, 302, 303, and 304, method 300 may be extendedto include further acts in order to, for example, fabricate some of theadditional elements and/or features described for sensors 100 and 200.For example, method 300 may include forming a second sensor electrode onthe second surface of the substrate, forming at least one electricallyconductive pathway that communicatively couples the at least a portionof at least one circuit and the second sensor electrode, and coating thesecond sensor electrode with the dielectric layer (either with a singlecontinuous dielectric layer or with a separate section of the dielectriclayer, as described previously). Either separately or in addition toforming a second sensor electrode, method 300 may include forming aground electrode on the second surface of the substrate and forming atleast one electrically conductive pathway that communicatively couplesthe ground electrode and the at least a portion of at least one circuit.In this case, coating the first sensor electrode with a dielectric layerper act 303 may include selectively coating the first sensor electrodewith the dielectric layer and not coating the ground electrode with thedielectric layer, or coating both the first sensor electrode and theground electrode with the dielectric layer and then forming a hole inthe dielectric layer to expose the ground electrode.

The improved capacitive EMG sensors described herein may be implementedin virtually any system, device, or process that makes use of capacitiveEMG sensors; however, the improved capacitive EMG sensors describedherein are particularly well-suited for use in EMG devices that areintended to be worn by (or otherwise coupled to) a user for an extendedperiod of time and/or for a range of different skin and/or environmentalconditions. As an example, the improved capacitive EMG sensors describedherein may be implemented in a wearable EMG device that providesgesture-based control in a human-electronics interface. Some details ofexemplary wearable EMG devices that may be adapted to include at leastone improved capacitive EMG sensor from the present systems, articles,and methods are described in, for example, U.S. Provisional PatentApplication Ser. No. 61/903,238; U.S. Provisional Patent ApplicationSer. No. 61/768,322 (now U.S. Non-Provisional patent application Ser.No. 14/186,889); Provisional Patent Application Ser. No. 61/771,500 (nowU.S. Non-Provisional patent application Ser. No. 14/194,252);Provisional Patent Application Ser. No. 61/857,105 (now U.S.Non-Provisional patent application Ser. No. 14/335,668); ProvisionalPatent Application Ser. No. 61/860,063 (now U.S. Non-Provisional patentapplication Ser. No. 14/276,575); Provisional Patent Application Ser.No. 61/866,960 (now U.S. Non-Provisional patent application Ser. No.14/461,044); Provisional Patent Application Ser. No. 61/869,526 (nowU.S. Non-Provisional patent application Ser. No. 14/465,194);Provisional Patent Application Ser. No. 61/881,064 (now U.S.Non-Provisional patent application Ser. No. 14/494,274); and ProvisionalPatent Application Ser. No. 61/894,263 (now U.S. Non-Provisional patentapplication Ser. No. 14/520,081), all of which are incorporated hereinby reference in their entirety.

Throughout this specification and the appended claims, the term“gesture” is used to generally refer to a physical action (e.g., amovement, a stretch, a flex, a pose, etc.) performed or otherwiseeffected by a user. Any physical action performed or otherwise effectedby a user that involves detectable muscle activity (detectable, e.g., byat least one appropriately positioned EMG sensor) may constitute agesture in the present systems, articles, and methods.

FIG. 4 is a perspective view of an exemplary wearable EMG device 400that includes improved capacitive EMG sensors in accordance with thepresent systems, articles, and methods. Exemplary wearable EMG device400 may, for example, form part of a human-electronics interface.Exemplary wearable EMG device 400 is an armband designed to be worn onthe forearm of a user, though a person of skill in the art willappreciate that the teachings described herein may readily be applied inwearable EMG devices designed to be worn elsewhere on the body of theuser, including without limitation: on the upper arm, wrist, hand,finger, leg, foot, torso, or neck of the user.

Device 400 includes a set of eight pod structures 401, 402, 403, 404,405, 406, 407, and 408 that form physically coupled links of thewearable EMG device 400. Each pod structure in the set of eight podstructures 401, 402, 403, 404, 405, 406, 407, and 408 is positionedadjacent and in between two other pod structures in the set of eight podstructures such that the set of pod structures forms a perimeter of anannular or closed loop configuration. For example, pod structure 401 ispositioned adjacent and in between pod structures 402 and 408 at leastapproximately on a perimeter of the annular or closed loop configurationof pod structures, pod structure 402 is positioned adjacent and inbetween pod structures 401 and 403 at least approximately on theperimeter of the annular or closed loop configuration, pod structure 403is positioned adjacent and in between pod structures 402 and 404 atleast approximately on the perimeter of the annular or closed loopconfiguration, and so on. Each of pod structures 401, 402, 403, 404,405, 406, 407, and 408 is physically coupled to the two adjacent podstructures by at least one adaptive coupler (not visible in FIG. 4). Forexample, pod structure 401 is physically coupled to pod structure 408 byan adaptive coupler and to pod structure 402 by an adaptive coupler. Theterm “adaptive coupler” is used throughout this specification and theappended claims to denote a system, article or device that providesflexible, adjustable, modifiable, extendable, extensible, or otherwise“adaptive” physical coupling. Adaptive coupling is physical couplingbetween two objects that permits limited motion of the two objectsrelative to one another. An example of an adaptive coupler is an elasticmaterial such as an elastic band. Thus, each of pod structures 401, 402,403, 404, 405, 406, 407, and 408 in the set of eight pod structures maybe adaptively physically coupled to the two adjacent pod structures byat least one elastic band. The set of eight pod structures may bephysically bound in the annular or closed loop configuration by a singleelastic band that couples over or through all pod structures or bymultiple separate elastic bands that couple between adjacent pairs ofpod structures or between groups of adjacent pairs of pod structures.Device 400 is depicted in FIG. 4 with the at least one adaptive couplercompletely retracted and contained within the eight pod structures 401,402, 403, 404, 405, 406, 407, and 408 (and therefore the at least oneadaptive coupler is not visible in FIG. 4).

Throughout this specification and the appended claims, the term “podstructure” is used to refer to an individual link, segment, pod,section, structure, component, etc. of a wearable EMG device. For thepurposes of the present systems, articles, and methods, an “individuallink, segment, pod, section, structure, component, etc.” (i.e., a “podstructure”) of a wearable EMG device is characterized by its ability tobe moved or displaced relative to another link, segment, pod, section,structure component, etc. of the wearable EMG device. For example, podstructures 401 and 402 of device 400 can each be moved or displacedrelative to one another within the constraints imposed by the adaptivecoupler providing adaptive physical coupling therebetween. The desirefor pod structures 401 and 402 to be movable/displaceable relative toone another specifically arises because device 400 is a wearable EMGdevice that advantageously accommodates the movements of a user and/ordifferent user forms.

Device 400 includes eight pod structures 401, 402, 403, 404, 405, 406,407, and 408 that form physically coupled links thereof. Wearable EMGdevices employing pod structures (e.g., device 400) are used herein asexemplary wearable EMG device designs, while the present systems,articles, and methods may be applied to wearable EMG devices that do notemploy pod structures (or that employ any number of pod structures).Thus, throughout this specification, descriptions relating to podstructures (e.g., functions and/or components of pod structures) shouldbe interpreted as being applicable to any wearable EMG device design,even wearable EMG device designs that do not employ pod structures(except in cases where a pod structure is specifically recited in aclaim).

In exemplary device 400 of FIG. 4, each of pod structures 401, 402, 403,404, 405, 406, 407, and 408 comprises a respective housing having arespective inner volume. Each housing may be formed of substantiallyrigid material and may be optically opaque. Throughout thisspecification and the appended claims, the term “rigid” as in, forexample, “substantially rigid material,” is used to describe a materialthat has an inherent tendency to maintain or restore its shape andresist malformation/deformation under the moderate stresses and strainstypically encountered by a wearable electronic device.

Details of the components contained within the housings (i.e., withinthe inner volumes of the housings) of pod structures 401, 402, 403, 404,405, 406, 407, and 408 are not necessarily visible in FIG. 4. Tofacilitate descriptions of exemplary device 400, some internalcomponents are depicted by dashed lines in FIG. 4 to indicate that thesecomponents are contained in the inner volume(s) of housings and may notnormally be actually visible in the view depicted in FIG. 4, unless atransparent or translucent material is employed to form the housings.For example, any or all of pod structures 401, 402, 403, 404, 405, 406,407, and/or 408 may include circuitry (i.e., electrical and/orelectronic circuitry). In FIG. 4, a first pod structure 401 is showncontaining circuitry 411 (i.e., circuitry 411 is contained in the innervolume of the housing of pod structure 401), a second pod structure 402is shown containing circuitry 412, and a third pod structure 408 isshown containing circuitry 418. The circuitry in any or all podstructures may be communicatively coupled to the circuitry in at leastone other pod structure by at least one communicative pathway (e.g., byat least one electrically conductive pathway and/or by at least oneoptical pathway). For example, FIG. 4 shows a first set of communicativepathways 421 providing communicative coupling between circuitry 418 ofpod structure 408 and circuitry 411 of pod structure 401, and a secondset of communicative pathways 422 providing communicative couplingbetween circuitry 411 of pod structure 401 and circuitry 412 of podstructure 402.

Throughout this specification and the appended claims the term“communicative” as in “communicative pathway,” “communicative coupling,”and in variants such as “communicatively coupled,” is generally used torefer to any engineered arrangement for transferring and/or exchanginginformation. Exemplary communicative pathways include, but are notlimited to, electrically conductive pathways (e.g., electricallyconductive wires, electrically conductive traces), magnetic pathways(e.g., magnetic media), and/or optical pathways (e.g., optical fiber),and exemplary communicative couplings include, but are not limited to,electrical couplings, magnetic couplings, and/or optical couplings.

Each individual pod structure within a wearable EMG device may perform aparticular function, or particular functions. For example, in device400, each of pod structures 401, 402, 403, 404, 405, 406, and 407includes a respective improved capacitive EMG sensor 410 (only onecalled out in FIG. 4 to reduce clutter) in accordance with the presentsystems, articles, and methods. Each improved capacitive EMG sensor 410is responsive to muscle activity corresponding to a gesture performed bya user of wearable EMG device 400. Thus, each improved capacitive EMGsensor 410 is included in device 400 to detect muscle activity of a userand to provide electrical signals in response to the detected muscleactivity. Thus, each of pod structures 401, 402, 403, 404, 405, 406, and407 may be referred to as a respective “sensor pod.” Throughout thisspecification and the appended claims, the term “sensor pod” is used todenote an individual pod structure that includes at least one sensor todetect muscle activity of a user.

Pod structure 408 of device 400 includes a processor 430 that processesthe signals provided by the improved capacitive EMG sensors 410 ofsensor pods 401, 402, 403, 404, 405, 406, and 407 in response todetected muscle activity. Pod structure 408 may therefore be referred toas a “processor pod.” Throughout this specification and the appendedclaims, the term “processor pod” is used to denote an individual podstructure that includes at least one processor to process signals. Theprocessor may be any type of processor, including but not limited to: adigital microprocessor or microcontroller, an application-specificintegrated circuit (ASIC), a field-programmable gate array (FPGA), adigital signal processor (DSP), a graphics processing unit (GPU), aprogrammable gate array (PGA), a programmable logic unit (PLU), or thelike, that analyzes or otherwise processes the signals to determine atleast one output, action, or function based on the signals. A person ofskill in the art will appreciate that implementations that employ adigital processor (e.g., a digital microprocessor or microcontroller, aDSP, etc.) may advantageously include a non-transitoryprocessor-readable storage medium or memory communicatively coupledthereto and storing processor-executable instructions that control theoperations thereof, whereas implementations that employ an ASIC, FPGA,or analog processor may or may optionally not include a non-transitoryprocessor-readable storage medium, or may include on-board registers orother non-transitory storage structures.

As used throughout this specification and the appended claims, the terms“sensor pod” and “processor pod” are not necessarily exclusive. A singlepod structure may satisfy the definitions of both a “sensor pod” and a“processor pod” and may be referred to as either type of pod structure.For greater clarity, the term “sensor pod” is used to refer to any podstructure that includes a sensor and performs at least the function(s)of a sensor pod, and the term processor pod is used to refer to any podstructure that includes a processor and performs at least thefunction(s) of a processor pod. In device 400, processor pod 408includes an improved capacitive EMG sensor 410 (not visible in FIG. 4)responsive to (i.e., to sense, measure, transduce or otherwise detectand provide one or more signal(s) in response to sensing, measuring,transducing, or otherwise detecting) muscle activity of a user, soprocessor pod 408 could be referred to as a sensor pod. However, inexemplary device 400, processor pod 408 is the only pod structure thatincludes a processor 430, thus processor pod 408 is the only podstructure in exemplary device 400 that can be referred to as a processorpod. The processor 430 in processor pod 408 also processes the EMGsignals provided by the improved capacitive EMG sensor 410 of processorpod 408. In alternative embodiments of device 400, multiple podstructures may include processors, and thus multiple pod structures mayserve as processor pods. Similarly, some pod structures may not includesensors, and/or some sensors and/or processors may be laid out in otherconfigurations that do not involve pod structures.

In device 400, processor 430 includes and/or is communicatively coupledto a non-transitory processor-readable storage medium or memory 440.Memory 440 may store processor-executable gesture identificationinstructions and/or data that, when executed by processor 430, causeprocessor 430 to process the EMG signals from improved capacitive EMGsensors 410 and identify a gesture to which the EMG signals correspond.For communicating with a separate electronic device (not shown),wearable EMG device 400 includes at least one communication terminal.Throughout this specification and the appended claims, the term“communication terminal” is generally used to refer to any physicalstructure that provides a telecommunications link through which a datasignal may enter and/or leave a device. A communication terminalrepresents the end (or “terminus”) of communicative signal transferwithin a device and the beginning of communicative signal transferto/from an external device (or external devices). As examples, device400 includes a first communication terminal 451 and a secondcommunication terminal 452. First communication terminal 451 includes awireless transmitter (i.e., a wireless communication terminal) andsecond communication terminal 452 includes a tethered connector port452. Wireless transmitter 451 may include, for example, a Bluetooth®transmitter (or similar) and connector port 452 may include a UniversalSerial Bus port, a mini-Universal Serial Bus port, a micro-UniversalSerial Bus port, a SMA port, a THUNDERBOLT® port, or the like.

For some applications, device 400 may also include at least one inertialsensor 460 (e.g., an inertial measurement unit, or “IMU,” that includesat least one accelerometer and/or at least one gyroscope) responsive to(i.e., to detect, sense, or measure and provide one or more signal(s) inresponse to detecting, sensing, or measuring) motion effected by a userand provide signals in response to the detected motion. Signals providedby inertial sensor 460 may be combined or otherwise processed inconjunction with signals provided by improved capacitive EMG sensors410.

As previously described, each of pod structures 401, 402, 403, 404, 405,406, 407, and 408 may include circuitry (i.e., electrical and/orelectronic circuitry). FIG. 4 depicts circuitry 411 inside the innervolume of sensor pod 401, circuitry 412 inside the inner volume ofsensor pod 402, and circuitry 418 inside the inner volume of processorpod 418. The circuitry in any or all of pod structures 401, 402, 403,404, 405, 406, 407 and 408 (including circuitries 411, 412, and 418) mayinclude any or all of: an amplification circuit to amplify electricalsignals provided by at least one EMG sensor 410, a filtering circuit toremove unwanted signal frequencies from the signals provided by at leastone EMG sensor 410, and/or an analog-to-digital conversion circuit toconvert analog signals into digital signals. Device 400 may also includeat least one battery (not shown in FIG. 4) to provide a portable powersource for device 400.

Each of EMG sensors 410 includes a respective improved capacitive EMGsensor per the present systems, articles, and methods, such as forexample sensor 100 from FIG. 1 or sensor 200 from FIG. 2. In particular,each EMG sensor 410 includes a respective first capacitive sensorelectrode 471 (only one called out to reduce clutter) that is coatedwith a dielectric layer formed of a dielectric material having arelative permittivity greater than or equal to about 10, a secondcapacitive sensor electrode 472 (only one called out to reduce clutter)that is also coated with a dielectric layer formed of a dielectricmaterial having a relative permittivity greater than or equal to about10, and a ground electrode 473 (only one called out to reduce clutter)that is exposed and not coated by a dielectric layer. Each theelectrodes 471, 472, and 473 of each EMG sensor 410 may be carried by arespective substrate, and the respective circuitry (e.g., 411, 412, and418) of each pod structure 401, 402, 403, 404, 405, 406, 407, and 408may be carried by the same substrate. For example, each respective EMGsensor 410 of each pod structure 401, 402, 403, 404, 405, 406, 407, and408 may include a respective substrate, with the circuitry 411, 412, 418of each pod structure 401, 402, 403, 404, 405, 406, 407, and 408 carriedby a first surface of the substrate and the first and second sensorelectrodes 471, 472 and the ground electrode 473 carried by a secondsurface of the substrate, the second surface being opposite the firstsurface.

The improved capacitive EMG sensors 410 of wearable EMG device 400 aredifferential sensors that each implement two respective sensorelectrodes 471, 472, though the teachings herein may similarly beapplied to wearable EMG devices that employ single-ended improvedcapacitive EMG sensors that each implement a respective single sensorelectrode.

Signals that are provided by improved capacitive EMG sensors 410 indevice 400 are routed to processor pod 408 for processing by processor430. To this end, device 400 employs a set of communicative pathways(e.g., 421 and 422) to route the signals that are output by sensor pods401, 402, 403, 404, 405, 406, and 407 to processor pod 408. Eachrespective pod structure 401, 402, 403, 404, 405, 406, 407, and 408 indevice 400 is communicatively coupled to, over, or through at least oneof the two other pod structures between which the respective podstructure is positioned by at least one respective communicative pathwayfrom the set of communicative pathways. Each communicative pathway(e.g., 421 and 422) may be realized in any communicative form, includingbut not limited to: electrically conductive wires or cables, ribboncables, fiber-optic cables, optical/photonic waveguides, electricallyconductive traces carried by a rigid printed circuit board, electricallyconductive traces carried by a flexible printed circuit board, and/orelectrically conductive traces carried by a stretchable printed circuitboard.

Device 400 from FIG. 4 represents an example of a wearable EMG devicethat incorporates the teachings of the present systems, articles, andmethods, though the teachings of the present systems, articles, andmethods may be applicable to any wearable EMG device that includes atleast one EMG sensor.

In accordance with the present systems, articles, and methods, acapacitive EMG sensor may be fabricated directly on a substrate that hasa high relative permittivity ε_(r), such as on a ceramic substrate. Forexample, referring back to sensor 200 of FIG. 2 using this alternativefabrication approach (which results in re-defining some of the labelledelements of FIG. 2), a capacitive EMG sensor 200 may comprise: asubstrate 250 that is formed of a material that has a high relativepermittivity (i.e., ε_(r) greater than or equal to about 10) such as aceramic material including but not limited to an X7R ceramic material,at least one sensor electrode 221, 231 deposited on and carried by thesubstrate 250, a dielectric layer 201 deposited on and carried by the atleast one sensor electrode 221, 231 and the substrate 250, circuitry 210deposited on and carried by the dielectric layer 201, and one or moreelectrically conductive pathway(s) (e.g., via(s)) that communicativelycouple the circuitry 210 to the at least one sensor electrode 221, 231.In this case, the substrate 250 may be thin (e.g., with a thickness ofabout 10 μm or less) and/or the at least one sensor electrode 221, 231may be deposited on the substrate 250 by first etching a trench into thesubstrate 250 (to a depth that leaves a thickness of 10 μm or less ofsubstrate material 250 beneath the trench) and then filling the trenchwith the sensor electrode material. If the sensor 200 further includes aground electrode 240, a hole 260 may be etched in the substrate 250 toexpose the ground electrode 240.

Throughout this specification and the appended claims, infinitive verbforms are often used. Examples include, without limitation: “to detect,”“to provide,” “to transmit,” “to communicate,” “to process,” “to route,”and the like. Unless the specific context requires otherwise, suchinfinitive verb forms are used in an open, inclusive sense, that is as“to, at least, detect,” to, at least, provide,” “to, at least,transmit,” and so on.

The above description of illustrated embodiments, including what isdescribed in the Abstract, is not intended to be exhaustive or to limitthe embodiments to the precise forms disclosed. Although specificembodiments of and examples are described herein for illustrativepurposes, various equivalent modifications can be made without departingfrom the spirit and scope of the disclosure, as will be recognized bythose skilled in the relevant art. The teachings provided herein of thevarious embodiments can be applied to other portable and/or wearableelectronic devices, not necessarily the exemplary wearable electronicdevices generally described above.

In the context of this disclosure, a memory is a processor-readablemedium that is an electronic, magnetic, optical, or other physicaldevice or means that contains or stores a computer and/or processorprogram. Logic and/or the information can be embodied in anyprocessor-readable medium for use by or in connection with aninstruction execution system, apparatus, or device, such as acomputer-based system, processor-containing system, or other system thatcan fetch the instructions from the instruction execution system,apparatus, or device and execute the instructions associated with logicand/or information.

In the context of this specification, a “non-transitoryprocessor-readable medium” can be any element that can store the programassociated with logic and/or information for use by or in connectionwith the instruction execution system, apparatus, and/or device. Theprocessor-readable medium can be, for example, but is not limited to, anelectronic, magnetic, optical, electromagnetic, infrared, orsemiconductor system, apparatus or device. More specific examples (anon-exhaustive list) of the processor-readable medium would include thefollowing: a portable computer diskette (magnetic, compact flash card,secure digital, or the like), a random access memory (RAM), a read-onlymemory (ROM), an erasable programmable read-only memory (EPROM, EEPROM,or Flash memory), a portable compact disc read-only memory (CDROM),digital tape, and other non-transitory media.

The various embodiments described above can be combined to providefurther embodiments. To the extent that they are not inconsistent withthe specific teachings and definitions herein, all of the U.S. patents,U.S. patent application publications, U.S. patent applications, foreignpatents, foreign patent applications and non-patent publicationsreferred to in this specification and/or listed in the Application DataSheet, including but not limited to U.S. Non-Provisional patentapplication Ser. No. 15/799,621; U.S. Non-Provisional patent applicationSer. No. 14/539,773; U.S. Provisional Patent Application Ser. No.61/903,238; U.S. Provisional Patent Application Ser. No. 61/768,322 (nowU.S. Non-Provisional patent application Ser. No. 14/186,889);Provisional Patent Application Ser. No. 61/771,500 (now U.S.Non-Provisional patent application Ser. No. 14/194,252); ProvisionalPatent Application Ser. No. 61/857,105 (now U.S. Non-Provisional patentapplication Ser. No. 14/335,668); Provisional Patent Application Ser.No. 61/860,063 (now U.S. Non-Provisional patent application Ser. No.14/276,575); Provisional Patent Application Ser. No. 61/866,960 (nowU.S. Non-Provisional patent application Ser. No. 14/461,044);Provisional Patent Application Ser. No. 61/869,526 (now U.S.Non-Provisional patent application Ser. No. 14/465,194); ProvisionalPatent Application Ser. No. 61/881,064 (now U.S. Non-Provisional patentapplication Ser. No. 14/494,274); and Provisional Patent ApplicationSer. No. 61/894,263 (now U.S. Non-Provisional patent application Ser.No. 14/520,081), are incorporated herein by reference, in theirentirety. Aspects of the embodiments can be modified, if necessary, toemploy systems, circuits and concepts of the various patents,applications and publications to provide yet further embodiments.

These and other changes can be made to the embodiments in light of theabove-detailed description. In general, in the following claims, theterms used should not be construed to limit the claims to the specificembodiments disclosed in the specification and the claims, but should beconstrued to include all possible embodiments along with the full scopeof equivalents to which such claims are entitled. Accordingly, theclaims are not limited by the disclosure.

1. A method of fabricating an electromyography (“EMG”) sensor, themethod comprising: forming at least a portion of at least one circuit ona first surface of a substrate; forming a first electrode on a secondsurface of the substrate, the second surface of the substrate oppositethe first surface of the substrate across a thickness of the substrate,wherein the first electrode comprises a first electrically conductiveplate; forming at least a first electrically conductive pathway throughthe substrate that communicatively couples the first electrode and theat least a portion of at least one circuit; forming a second electrodeon the second surface of the substrate, wherein the second electrodecomprises a second electrically conductive plate; forming at least asecond electrically conductive pathway through the substrate thatcommunicatively couples the second electrode and the at least a portionof at least one circuit.
 2. The method of claim 1 wherein forming afirst electrode on a second surface of the substrate includes forming afirst sensor electrode on the second surface of the substrate.
 3. Themethod of claim 2 wherein forming a second electrode on a second surfaceof the substrate includes forming a ground electrode on the secondsurface of the substrate.
 4. The method of claim 2 wherein forming asecond electrode on a second surface of the substrate includes forming asecond sensor electrode on the second surface of the substrate.
 5. Themethod of claim 4, further comprising: forming a ground electrode on thesecond surface of the substrate, wherein the ground electrode comprisesa third electrically conductive plate; and forming at least a thirdelectrically conductive pathway through the substrate thatcommunicatively couples the ground electrode and the at least a portionof at least one circuit.
 6. The method of claim 1 wherein forming afirst electrode on a second surface of the substrate and forming asecond electrode on the second surface of the substrate include formingthe first electrode and the second electrode coplanar to one another onthe second surface of the substrate.
 7. The method of claim 1 whereinforming at least a portion of at least one circuit on a first surface ofa substrate includes forming, on the first surface of the substrate, atleast a portion of at least one circuit selected from a group consistingof: an amplification circuit, a filtering circuit, and ananalog-to-digital conversion circuit.